Handling of timers

ABSTRACT

System, methods, entities, and computer program for handling timers in a communication network are described. The communication network comprises a plurality of entities ( 100 - 108 ). The method in a first entity ( 100 ) comprises determining ( 301 ) whether a supervision condition for supervising a communication procedure is fulfilled. The method further comprises adding ( 308 ), based on a result of the step of determining the supervision condition ( 301 ), a timer validity information to a signaling message related to the communication procedure, and sending ( 308 ) the signaling message to a second entity ( 102 ). The method in a second entity ( 102 - 108 ) comprises receiving ( 400 ) a signaling message associated with a communication procedure, the signaling message containing a timer validity information. The method further comprises determining ( 401 ) whether a further processing condition for performing further steps of the communication procedure is fulfilled, the further processing condition being associated with the timer validity information. The system, entities ( 100 - 108 ) and computer program associated with these methods are also described. Therefore an improved handling of time supervisions in a communication network is achieved in terms of accuracy of supervision timeout, and eliminating a triggering of unwanted remote actions after local timeout.

TECHNICAL FIELD

The present invention relates to telecommunications and in particular tosystem methods, nodes and computer program for handling timers in acommunication network.

BACKGROUND

Timers are widely used in communication networks to supervisecommunication procedures and signaling exchange between entities of thecommunication network based on protocols. An example of such entitiesmay be a Call Session Control Function, CSCF, being an essential node inan IP Multimedia System, IMS, for processing signaling, using a SessionInitiation Protocol, SIP, as the signaling protocol. CSCF handlessession establishment, modification and release of IP multimediasessions using the SIP/Session Description Protocol, SDP, protocolsuite. A 3rd Generation Partnership Project, 3GPP TechnicalSpecification, TS 23.228 describes logical nodes Proxy P-CSCF,Interrogating I-CSCF, Serving S-CSCF, Emergency E-CSCF and BorderGateway Control Function, BGCF.

The S-CSCF conforms to 3GPP TS 24.229 specification and performs thesession control services for a User Equipment, UE. It maintains asession state for support of the services requested by and offered tothe UE.

The S-CSCF performs for example the following functions:

-   -   Acts as a registrar according to RFC3261 at registration    -   Notify subscribers about registration changes    -   Session control for the registered user's sessions    -   Handles SIP requests and services them internally or forwards        them    -   Interaction with application servers

An S-CSCF performs SIP routing according to the 3GPP routing procedures.

RFC 3261 defines SIP timers for supervising the lifetime of atransaction within the network. Dependent on what type of request(non-INVITE or INVITE request) or response (successful or notsuccessful) and what type of transport protocol is used (User DatagramProtocol, UDP or Transmission Control Protocol, TCP) different SIPtimers are used.

Following SIP transaction timers are applicable within the CSCF:

-   -   Timer T1—Round-Trip Time estimate

Timer T1 is used to supervise transactions at UDP transport. The timeris configurable. The value shall be the estimated round-trip time. CSCFdoes not directly use T1 as a timer, T1 is instead used to calculate thetimers A, B, E, F, G, H and J.

-   -   Timer T2—Maximum retransmit interval for non-INVITE requests and        INVITE responses

Timer T2 defines the maximum retransmission interval for non-INVITErequests and INVITES responses. The T2 value is used as a maximum valuefor timer E and timer G.

-   -   Timer T4—Maximum duration a message will remain in the network

Timer T4 defines the maximum duration a message will remain in thenetwork. The timer is configurable. The value T4 is used as a value fortimer I and timer K.

-   -   Timer A—INVITE request retransmit interval for UDP only    -   Timer B—INVITE transaction timeout timer    -   Timer C—Proxy INVITE transaction timeout    -   Timer D—wait time for response retransmits    -   Timer E—non-INVITE request retransmit interval for UDP only    -   Timer F—Maximum waiting time for final response for a non-INVITE        transaction    -   Timer G—INVITE response retransmit interval    -   Timer H—wait time for ACK receipt after 3xx-6xx SIP responses    -   Timer I—wait time for ACK retransmits    -   Timer J—Maximum waiting time for request re-transmits for a        non-INVITE request    -   Timer K—Waiting time for response retransmits for non-INVITE        requests

Timers are started hop-by-hop at each entity that needs to keep track ofa transaction.

In IMS using SIP as mechanism of signaling communication, transactionsare monitored hop-by-hop by the entities that are involved in thecommunication chain. This means that timers are started for differenttype of information to be sent or received to keep track of the validlifetime, so re-transmission or canceling of the transaction can beperformed as appropriate.

In the communication between entities there could be several entitiesincluded and each of them has own timer settings local to the specificentity. Relations in timer settings between entities are usuallyconfigured and coordinated manually and there is no logic in theentities of informing its own peers what they will use for a givencommunication procedure.

As between entities, entities keep track of their own timers only,communication procedures can get out-of-sync for communicationtraversing a network and timers time-out in one entity within the chainbefore the response has been received.

There could also be race condition occurring when timers are expired andcommunications related to the same sessions are competing through thenetwork to reach its destination.

In large networks with multiple destinations as alternative routingpaths, timer relations really matters if the configured paths will everbe tried before the timer in previous hops expired.

For services involving serial forking of communication to multiplecontacts the timer knowledge is of interest to know how long it issufficient to wait before canceling a request. In a worst case, a newforking is done at a remote entity, although a local timer for therelated communication procedure has expired already.

SUMMARY

It is an object of the invention to provide measures with which handlingof timers in a communication is improved in terms of accuracy ofsupervision timeout, and triggering of unwanted remote actions afterlocal timeout. It is also an object of the invention to providecorresponding methods, nodes, and computer programs.

The objects defined above are solved by the features of the independentclaims. Preferred embodiments of the invention are described in thedependent claims.

According to an exemplary aspect of the invention, a method for handlingtime supervision in a communication network comprising a plurality ofentities is provided. The method comprises determining, by a firstentity, whether a supervision condition for supervising a communicationprocedure is fulfilled. The method comprises, based on a result of thestep of determining the supervision condition, adding, by the firstentity, a timer validity information to a signaling message related tothe communication procedure, and sending the signaling message to asecond entity to be involved in the communication procedure.

The method may further comprise that the supervision condition isassociated with a type of the communication procedure and is involvingat least one further entity of the plurality of entities in thecommunication network.

According to another exemplary aspect of the invention, a method forhandling time supervision in a communication network comprising aplurality of entities is provided. The method comprises receiving, by asecond entity, a first signaling message associated with a communicationprocedure from a first entity, the first signaling message containing afirst timer validity information. The method comprises, determining, bythe second entity, whether a further processing condition for performinga further step of the communication procedure is fulfilled, the furtherprocessing condition being associated with the first timer validityinformation.

The method may further comprise, that the further step of thecommunication procedure is any one of the following steps: Sending, bythe second entity, a further signaling message associated with thecommunication procedure to a further entity of the plurality of entitiesof the communication network, the further signaling message containing afurther timer validity information. Sending, by the second entity, afurther signaling message associated with a further communicationprocedure to a further entity of the plurality of entities of thecommunication network, the further signaling message containing afurther timer validity information. Sending, by the second entity, aresponse to the first signaling message to the first entity, or,terminating, by the second entity, the communication procedure.

The method may further comprise, that, if a supervision period of thefurther signaling message expires before expiration of the first timervalidity information, the second timer validity information is set equalto a current time plus a supervision period of the further signalingmessage, else, the second timer validity information is set equal to thefirst timer validity information.

According to another exemplary aspect of the invention, a network entityfor handling time supervision in a communication network comprising aplurality of entities, the network entity being capable of determiningwhether a communication procedure is to be started which requires timesupervision. The network entity being further capable of determining acurrent time and determining a time supervision period associated withthe communication procedure. The network entity being further capable ofsending a signaling message related to the communication procedure, thesignaling message comprising the timer validity information based on thecurrent time and the time supervision period. The network entity beingfurther capable of time supervising the reception of a response to thesignaling message. The network entity being further capable ofterminating the communication procedure at expiry of the timesupervision period. The network entity being further capable offinishing the communication procedure the reception of a response to thesignaling message.

According to another exemplary aspect of the invention, a network entityfor handling time supervision in a communication network comprising aplurality of entities, the network entity being capable of receiving afirst signaling message related to a communication procedure, the firstsignaling message comprising a first timer validity information. Thenetwork entity being further capable of determining a further step ofthe communication procedure. The network entity being further capable ofdetermining a current time and determining a time supervision periodassociated with a further signaling message related to the communicationprocedure or to a further communication procedure. The network entitybeing further capable of determining a second timer validity informationbased on the current time and a time supervision period for the furthersignaling message. The network entity being further capable of sendingthe further signaling message to a further entity in the communicationsystem, the further signaling message comprising the timer validityinformation. The network entity being further capable of timesupervising the reception of a response to the further signalingmessage. The network entity being further capable of terminating thecommunication procedure at expiry of the first timer validityinformation. The network entity being further capable of determiningthat a remaining time period before expiry of the first timer validityinformation reaches a threshold. The network entity being furthercapable of sending a response associated with the first signalingmessage related to the communication procedure, based on the receptionof a response to the further signaling message.

According to another exemplary aspect of the invention, a system forhandling time supervision in a communication network comprising aplurality of entities, the system comprising a first entity and at leastone second entity.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent in the following detaileddescription of embodiments of the invention illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the detailed description of particular but notexclusive embodiments, illustrated by way of non-limiting examples inthe accompanying drawings, wherein:

FIG. 1 is block diagram illustrating a system for handling timersaccording to an embodiment of the invention;

FIG. 2 is a procedure flow diagram illustrating the forwarding of timervalidity information according to an embodiment of the invention;

FIG. 3 is a flow diagram illustrating a method in a first entity forhandling timers according to an embodiment of the invention;

FIG. 4 is a flow diagram illustrating a first method in a second entityfor handling timers according to an embodiment of the invention;

FIG. 5a is a flow diagram illustrating a second method in a secondentity for handling timers according to an embodiment of the invention;

FIG. 5b is a flow diagram illustrating a third method in a second entityfor handling timers according to an embodiment of the invention;

FIG. 6 is a flow diagram illustrating a fourth method in a second entityfor handling timers according to an embodiment of the invention;

FIG. 7 is a procedure flow diagram illustrating the handling at expiryof timer validity according to an embodiment of the invention;

FIG. 8 is a procedure flow diagram illustrating the handling when timervalidity expires soon according to an embodiment of the invention;

FIG. 9 is a block diagram illustrating a first entity for handlingtimers according to an embodiment the invention; and

FIG. 10 is a block diagram illustrating a second entity for handlingtimers according to an embodiment the invention.

DETAILED DESCRIPTION

In the following, methods and network entities for handling timers andassociated computer programs according to the invention are described inmore detail.

Within the context of the present application, the term “communicationnetwork” may particularly denote a collection of nodes or entities,related transport links, and associated management needed for running aservice, for example a telephony service or a packet transport service.Depending on the service, different node types or entities may beutilized to realize the service. A network operator owns thecommunication network, and offers the implemented services to itssubscribers. Typical examples of a communication network are radioaccess network, mobile backhaul network, or core network.

The term “entity” may particularly refer to a node in the communicationnetwork or to a UE attached to such communication network. It may referto any handling element in a communication procedure that can initiatesuch a communication procedure, receive it, or forward it. In a widercontext, the term “entity” may also particularly refer to softwareinstances, computer processes, or virtual machines communicating witheach other.

The term “timer validity” may particularly refer to an informationelement wherein the timer validity information indicates an absolutepoint in time comprising year, date, time, and time zone information. Anexample of such timer validity may be an information element coded in aCoordinated Universal Time, UTC, format. This format, for example,comprises information such as:

Year:

YYYY (eg 1997)

Year and month:

YYYY-MM (eg 1997-07)

Complete date:

YYYY-MM-DD (eg 1997-07-16)

Complete date plus hours and minutes:

YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)

Complete date plus hours, minutes and seconds:

YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)

Complete date plus hours, minutes, seconds and a decimal fraction of asecond:

YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)

where:

YYYY=four-digit year

MM=two-digit month (01=January, etc.)

DD=two-digit day of month (01 through 31)

hh=two digits of hour (00 through 23) (am/pm NOT allowed)

mm=two digits of minute (00 through 59)

ss=two digits of second (00 through 59)

s=one or more digits representing a decimal fraction of a second

TZD=time zone designator (Z or +hh:mm or −hh:mm)

Further information on coding of information elements indicating anabsolute point in time can also be found in the W3C document “Date andTime Formats”, or in ISO 8601, the International Standard for therepresentation of dates and times. UTC is defined by InternationalTelecommunications Union Recommendation ITU-R TF.460-6.

Referring to FIG. 1, a system for handling time supervision in acommunication network according to an embodiment is shown.

The communication network comprises a plurality of entities 100-108,wherein in FIG. 1 three entities 100, 102, 104 are show in order toexemplify the principle of handling a communication procedure in acommunication network. The entities 100, 102, 104 are interconnected bytransport links in such a way that the first entity 100 can communicatewith the second entity 102. In the same manner, the second entity 102can communicate with a third entity 104, and so on. On a logical level,the plurality of entities 100-108 of the communication network cancommunicate with each other, so any single entity 100-108 cancommunicate with any other single entity 100-108 of the plurality ofentities 100-108 of the communication network.

For example, the entities 100-108 may be network nodes such as a MobileSwitching Center, MSC, or a CSCF, or a Serving Gateway Support Node,SGSN, or a Mobility Management Entity, MME, or a User Equipment, UE.

The first entity 100 determines 300 whether a supervision condition forsupervising a communication procedure is fulfilled. Based on a result ofthe step of determining 301 the supervision condition, adding 308, bythe first entity 100, a timer validity information to a signalingmessage related to the communication procedure, and sending thesignaling message to a second entity 102 to be involved in thecommunication procedure. Here the second entity 102 may bepre-determined by the type of communication procedure, so the firstentity 100 does not have to select the second entity 102. Byalternative, the first entity 100 may select the second entity 102 andbased on this selection the first entity 100 involves the second entity102 in the communication procedure. This selection may be done based ona load sharing algorithm, may by alternative be based on operatorpre-configuration by operation and maintenance means, or, may also bebased on a routing decision in the first entity 100.

In this scenario the first entity 100 may add a single timer validityinformation to the signaling message. By alternative, the first entity100 may add multiple instances of timer validity information to thesignaling message. In this case each instance of the timer validityinformation may correspond to a different step of the communicationprocedure, or may also refer to different communication procedures.

The supervision condition may be associated with a type of thecommunication procedure and is involving at least one further entity100-104 of the plurality of entities 100-104 in the communicationnetwork. In a typical entity 100-104, several communication proceduresrun in parallel, and an entity 100-104 may also contain internallysub-entities, which may also communicate with each other. In contrast tothis entity internal communication, here it is referred to communicationbetween entities 100-104 and therefore the communication procedureinvolves at least one further entity 100-104 of the plurality ofentities 100-104 in the communication network.

Subsequent to the sending of the signaling message related to thecommunication procedure containing the timer validity information, thefirst entity 100 determines, whether a termination condition fortermination of the communication procedure is fulfilled. In the samemanner as there is a condition to start a communication procedure in thefirst entity 100, there is a condition when the communication procedureis finished or has to be terminated.

So based on a result of the step of determining the terminationcondition, the first entity 100 may terminate the running communicationprocedure. The termination condition may be associated with a receptionof a response to the signaling message sent to the second entity 102 orwith an expiry of a supervision timer supervising the reception of theresponse to the sent signaling message.

Also a second entity 102 performs a method for handling time supervisionin a communication network comprising a plurality of entities 100-104.The second entity 102 may be the second entity 102 of FIG. 1. The methodin the second entity 102 comprises the receiving, of a first signalingmessage associated with a communication procedure from a first entity100, the first signaling message containing a first timer validityinformation.

The method in the second entity 102 comprises further the determining,whether a further processing condition for performing a further step ofthe communication procedure is fulfilled, the further processingcondition being associated with the first timer validity information. Acommunication procedure, after the communication procedure start hasbeen triggered, comprises a number of steps. These steps may compriseconsecutive steps to be performed in a certain order, or as analternative, may comprise alternative step options. So if a furtherprocessing condition has been reached a decision is taken, which of thealternative further steps of the communication procedure to take, orwhether to perform the next consecutive steps of the communicationprocedure.

So the further step of the communication procedure may be any one of thefollowing steps, performed by the second entity 102. The second entity102 may send 414 a further signaling message associated with thecommunication procedure to a further entity 100-104 of the plurality ofentities 100-104 of the communication network, the further signalingmessage containing a further timer validity information. In this casethe communication procedure is continued to a further entity 100-104,which may be a third entity 104 of FIG. 1.

The second entity 102 may send 414 a further signaling messageassociated with a further communication procedure to a further entity100-104 of the plurality of entities 100-104 of the communicationnetwork, the further signaling message containing a further timervalidity information. In this case a new communication procedure isstarted by the second entity 102, which involves a third entity 104,which may be the third entity 104 of FIG. 1.

The second entity 102 may send 512 a response to the first signalingmessage to the first entity 100. In this case the task of thecommunication procedure may be completed and a response may be returnedto the entity 100 originating the communication procedure. It may alsobe the case that an error has occurred during the execution of thecommunication procedure and the response contains an indication of theoccurred error.

The second entity 102 may terminate 504 the communication procedure. Inthis case the communication procedure may be ended without informing theentity 100 originating the communication procedure. This may happen iffor example a severe error has happened in the handling by entity 102,or if the communication procedure has been pending for too long withoutprogress in the steps of the communication procedure.

The further processing condition in the second entity 102 is associatedwith any one of the following conditions. An expiry 416 of a supervisiontimer supervising the reception of a response to a signaling messageassociated with the communication procedure, before expiry of the firsttimer validity information. So in case the further step of thecommunication procedure involves the sending of a signaling message to athird entity 104, the response to this signaling message is supervisedby a timer. So the expiry of this supervision timer triggers the furtherprocessing condition.

The first timer validity information may expire 502 in the second entity102 and this triggers the further processing condition.

The second entity 102 may receive 510 a response to a signaling messageassociated with the communication procedure, before expiry of the firsttimer validity information. So in case the further step of thecommunication procedure involves the sending of a signaling message to athird entity 104, a corresponding response is received and this triggersthe further processing condition.

The second entity 102 may determine 602 that a remaining time periodbefore expiry of the first timer validity information reaches athreshold. So in case the further step of the communication procedureinvolves the sending of a signaling message to a third entity 104, theresponse to this signaling message is supervised by a timer. In thiscase the further processing condition is triggered when remaining timeperiod before expiry of the first timer validity information reaches athreshold.

This threshold may be based on a signaling delay time for a signalingmessage to traverse between the first entity 100 and the second entity102 of the communication network. The signaling delay time may relate toa propagation delay of a transport link between the entities 100-104,plus the processing time of transiting entities transiting a signalingmessage between the first entity 100 and the second entity 102 of thecommunication network. Also the processing time in the first entity 100and the second entity 102 add to the overall signaling delay time for asignaling message. So the threshold may be chosen in such a way that thefurther processing condition is triggered well in time so that aresponse sent from the second entity 102 to the first entity 100 reachesthe first entity 100 before the expiry of the timer validity in thefirst entity 100.

As described, second entity 102 may subsequent to the step of receivingthe first signaling message, send a second signaling message associatedwith the communication procedure to a further entity 100-104 of theplurality of entities 100-104 of the communication network, the secondsignaling message containing a second timer validity information. So thesecond entity 102 may send a signaling message to a third entity 104, orin another step to a fourth entity 106, and so on. A fourth entity 106is not depicted in FIG. 1, but it shall be understood that thecommunication procedure may involve more than three entities. So thecommunication procedure may be continued to a fourth entity 106, or anew communication procedure is started towards a fourth entity 106, orthe third entity 104 first sends a signaling message to a fourth entity106, and then sends another signaling message to a fifth node 108. Sofor a person skilled in the art it is clear that the methods performedby the second entity 102 may in a equivalent way also be applied in athird node 104, a fourth node 106, and so on. For simplicity reasonsFIG. 1 is limited to three entities 100, 102, 104.

Referring to FIG. 2, a method in a system for handling time supervisionin a communication network will be explained.

As described above, for a person skilled in the art it is clear that themethods performed by the second entity 102 may in a similar way also beapplied in a third node 104, a fourth node 106, and so on. FIG. 2 showsan example of a communication network wherein a communication procedureinvolves five entities 100-108 in a consecutive order. This example maybe well suited to explain the handling of the timer validity informationin relation to an absolute time, a signaling delay, and a communicationprocedure. In this scenario the entity 1 may perform the method of thefirst entity 100, while entity 2 102 to entity 5 108 may perform themethod of the second entity 102.

The communication procedure may be started in entity 1 100 at a time 200of 11:20:00, referring to 11 o'clock, 20 minutes and zero seconds. Thecommunication procedure may to be time supervised and the relatedsupervision timer 202 is 30 s referring to 30 seconds. A correspondingsignaling message 204 called “Start Procedure” may be sent from entity 1100 to entity 2 102. Entity 1 102 may include the timer validityinformation into the signaling message 204. In this case thecommunication procedure may be valid from 11:20:00 for 30 seconds. Soentity 1 100 may await a corresponding response to the signaling message204 called “Start Procedure” within the time supervision period. Thetimer validity information may be set to 11:20:30 by entity 1 100 andmay be added by entity 1 100 to the signaling message, which maycorrespond to the current time of 11:20:00 plus the 30 s timesupervision period.

In the next step entity 2 102 may receive the signaling message 204called “Start Procedure”. It may contain the timer validity informationset to 11:20:30. As a signaling delay of one second between entity 1 andentity 2 is assumed, the signaling message may arrive 206 at 11:20:01time. Entity 2 102 may continue the communication procedure to theentity 3 104, by sending a signaling message 210 called “ContinueProcedure”. Entity 2 102 may supervise the communication procedure andthe related supervision timer 208 may be 20 s. So the timer validityinformation added by entity 2 102 to the signaling message 210 “ContinueProcedure” may be set to 11:20:21.

In the next step entity 3 104 may receive the signaling message 210called “Continue Procedure”. It may contain the timer validityinformation set to 11:20:21. As a signaling delay of one second betweenentity 2 102 and entity 3 104 is assumed, the signaling message mayarrive 212 at 11:20:02 time. Entity 3 104 may continue the communicationprocedure to the entity 4 106, by sending a signaling message 216 called“Continue Procedure”. Entity 3 104 may supervise the communicationprocedure and the related supervision timer 214 may be 15 s. So thetimer validity information added by entity 3 104 to the signalingmessage 216 “Continue Procedure” may be set to 11:20:17.

In the next step entity 4 106 may receive the signaling message 216called “Continue Procedure”. It may contain the timer validityinformation set to 11:20:17. As a signaling delay of one second betweenentity 3 104 and entity 4 106 is assumed, the signaling message mayarrive 218 at 11:20:03 time. Entity 4 106 may continue the communicationprocedure to the entity 5 108, by sending a signaling message 222 called“Continue Procedure”. Entity 4 106 may supervise the communicationprocedure and the related supervision timer 220 may be 10 s. So thetimer validity information added by entity 4 106 to the signalingmessage 222 “Continue Procedure” may be set to 11:20:13.

In the next step entity 5 108 may receive the signaling message 222called “Continue Procedure”. It may contain the timer validityinformation set to 11:20:13. As a signaling delay of one second betweenentity 4 and entity 5 is assumed, the signaling message may arrive at11:20:04 time. The communication procedure may end in entity 5 108, andentity 5 108 may return a corresponding response message 224 called“Procedure Response”.

The response message 224, 226, 228, 230 called “Procedure Response” maybe transited via entity 4 106, entity 3 104, and entity 2 102 to entity1 100 and the communication procedure may end successfully.

In this scenario the entity 2 102 to entity 4 106 may perform the methodof the second entity 102. So if a supervision period of the outgoingsignaling message expires before expiration of the received timervalidity information, the outgoing timer validity information may be setequal to a current time plus a supervision period of the outgoingsignaling message.

Referring to FIG. 3, a method in a first entity 100 for handling timesupervision in a communication network will be explained.

In step 300 a communication procedure may have to be started and it maybe determined in step 301 whether a supervision condition forsupervising the communication procedure is fulfilled, so whether thecommunication procedure shall be time supervised.

If so, in step 302 the current time may be determined. This may be doneby reading a system clock integrated into the hardware platform of thefirst entity 100. By alternative, the current time may be fetched from acentral Network Time Protocol (NTP) Server belonging to thecommunication network infrastructure, or belonging to the Internet. Thereceived time information may still have to be adjusted to the localtime zone of the first entity 100.

In the next step, 304, a time supervision period for a signaling messagerelated to the communication procedure may be determined. Typically, thetime supervision period may be defined by the relevant protocol orprocedure specification. By alternative, the time supervision period mayalso be pre-defined by operation and maintenance means by the operatorof the first entity 100. Steps 302 and 304 may also be performed indifferent order, step 304 first and then 302.

In step 306 the time supervision may be started, using the timesupervision period as determined in step 304. This may typically be atimer running in the hardware platform of the entity 100 or a countercounting a periodical interrupt of the processor.

In step 308 the signaling message may be sent out, including the timervalidity information, here called T_v. T_v is based on the current time,here called T_c and the supervision period, here called T_s. So T_v iscalculated by the equation T_v=T_c+T_s.

After having sent out the signaling message to the second entity 102,the supervision of the communication procedure may start. A loop may bestarted that first checks in step 310 whether a response to the sentsignaling message has been received. If this is not the case, it may bechecked in 312 whether the supervision time T_v has expired. If this isnot the case, the loop may be repeated with step 310.

There may be two ways to exit the supervision of the communicationprocedure. The first may be the reception of a response to the sentsignaling message in step 310. This leads to step 316, where thecommunication procedure is set to “finished” and the flow stops.

The second loop exit criteria may be the expiry of the supervision timeT_v. This may lead to step 314, where the communication procedure isterminated and the flow stops.

Referring to FIG. 4, a first method in a second entity 102 for handlingtime supervision in a communication network will be explained.

In step 400 a signaling message related to a communication procedure maybe received in a second entity 102. The signaling message may contain atimer validity information T_v, which corresponds to a first timervalidity information.

In step 401 the next step of the communication procedure may bedetermined. In this example it is assumed that the second entity 102will continue the communication procedure to a further entity by sendinga signaling message to the further entity, and the outgoing signalingmessage shall contain a corresponding timer validity informationT_v_out, which corresponds to a second timer validity information.

So, in step 402 the current time may be determined. This may be done byreading a system clock integrated into the hardware platform of thesecond entity 102. By alternative, the current time may be fetched froma central Network Time Protocol (NTP) Server belonging to thecommunication network infrastructure, or belonging to the Internet. Thereceived time information may still have to be adjusted to the localtime zone of the second entity 102.

In the next step, 404, a time supervision period for a signaling messagerelated to the communication procedure may be determined. Typically, thetime supervision period may be defined by the relevant protocol orprocedure specification. By alternative, the time supervision period mayalso be pre-defined by operation and maintenance means by the operatorof the second entity 102. Steps 402 and 404 may also be performed indifferent order, step 404 first and then 402.

In the step 406 the timer validity information T_v_out for the outgoingsignaling message may be determined, based on the current time T_c andthe supervision period T_s. For this it may be checked in step 406,whether the sum of T_c and T_s is larger than the received T_v. If asupervision period of the further signaling message expires beforeexpiration of the first timer validity information, the second timervalidity information is set equal to a current time plus a supervisionperiod of the further signaling message, else, the second timer validityinformation is set equal to the first timer validity information. SoT_v_out is either T_c+T_s, or else T_v_out is set to T_v.

In step 412 the time supervision of T_v_out may be started. This may betypically a timer running in the hardware platform of the entity or acounter counting a periodical interrupt of the processor.

In step 414 the signaling message may be sent out to the further entity,including the determined timer validity information T_v_out and flowstops. This signaling message may be a continuation of the communicationprocedure related to the signaling message received in step 400, or byalternative, the signaling message may be related to a new communicationprocedure started by this signaling message.

After having sent out the signaling message to the further entity,several further steps of the communication procedure may have to betaken. One possible step may be triggered by the expiry of the T_v_outsupervision timer in step 416.

In this example it is assumed that the second entity 102 will continuethe communication procedure to a further entity by sending a signalingmessage to the further entity, and the outgoing signaling message shallcontain a corresponding timer validity information T_v_out, whichcorresponds to a second timer validity information. So the steps 401 to414 may be executed again and a new outgoing timer validity informationT_v_out may be determined as described above.

Referring to FIG. 5a , a second method in a second entity 102 forhandling time supervision in a communication network will be explained.

In step 500 the second entity 102 may monitor the supervision timer T_vreceived from the first entity 100.

In step 502 it may be determined whether the supervision timer T_v hasexpired. If not, a loop may be done and the monitoring continues withstep 500.

If the supervision timer T_v is expired, in step 504 the communicationprocedure may be terminated and the flow stops. No response is returnedto the first entity 100.

Referring to FIG. 5b , a third method in a second entity 102 forhandling time supervision in a communication network will be explained.

In step 510 the second entity 102 may receive a final response for theongoing communication procedure.

In step 512 the final response for the ongoing communication proceduremay be returned to the first entity 100.

Finally the communication procedure may be finished in step 514 and theflow may stop.

Referring to FIG. 6, a fourth method in a second entity 102 for handlingtime supervision in a communication network will be explained.

In step 600 the second entity 102 may monitor the supervision timer T_vreceived from the first entity 100.

In step 602 it may be determined whether the supervision timer T_v willexpire soon. If not, a loop is done and the monitoring continues withstep 600.

If the supervision timer T_v will expire soon, so a remaining timeperiod before expiry of the timer T_v reaches a threshold, step 604 maybe performed. In this example it is assumed that a signaling message maybe sent to a default destination if the supervision timer T_v willexpire soon. However, also other default steps of the communicationprocedure could be applied.

So, in step 604 the current time T_c may be determined. This may be doneby reading a system clock integrated into the hardware platform of thesecond entity 102. By alternative, the current time can be fetched froma central Network Time Protocol (NTP) Server belonging to thecommunication network infrastructure, or belonging to the Internet. Thereceived time information may still have to be adjusted to the localtime zone of the second entity 102.

In the next step, 606, a time supervision period for a signaling messagerelated to the communication procedure may be determined. Typically, thetime supervision period is defined by the relevant protocol or procedurespecification. By alternative, the time supervision period may also bepre-defined by operation and maintenance means by the operator of thesecond entity 102. Steps 604 and 606 may also be performed in differentorder, step 606 first and then 604.

In step 608 the time supervision may be started. This may typically be atimer running in the hardware platform of the entity or a countercounting a periodical interrupt of the processor.

In step 610 the signaling message may be sent out, continuing thecommunication procedure to a default destination and the flow stops.

The signaling message to the default destination may also include thetimer validity information. In this case a T_v_out timer validityinformation is determined in the same way as described above. Asignaling message to a default destination may also omit timer validityinformation if the default destination cannot handle this information.

Referring to FIG. 7, a method in a system for handling time supervisionin a communication network will be explained.

This scenario shows a case where an entity sequentially forwardssignaling messages to different destinations, trying to find adestination that responds to the signaling message in time. This may bean example for delivering a telephone call to a subscriber with multipledevices. The telephone call is delivered to the first device, and if thesubscriber does not answer on this device, the telephone call isdelivered to the next device, and so on until the subscriber answers ona device, or a time supervision for delivery of the telephone callexpires.

FIG. 7 shows an example of a communication network wherein acommunication procedure involves four entities 100-106. In this scenariothe entity 1 100 performs the method of a first entity 100, while entity2 102 and entity 3 104 perform the method of a second entity 102.

The communication procedure is started in entity 1 100 at a time 700 of11:20:00, referring to 11 o'clock, 20 minutes and zero seconds. Thecommunication procedure is to be time supervised and the relatedsupervision timer 702 is 30 s referring to 30 seconds. A correspondingsignaling message 704 called “Start Procedure” may be sent from entity 1100 to entity 2 102. Entity 1 100 may include the timer validityinformation into the signaling message 704. In this case thecommunication procedure may be valid from 11:20:00 for 30 seconds. Soentity 1 100 may await a corresponding response to the signaling message704 called “Start Procedure” within the time supervision period. Thetimer validity information set by entity 1 100 and added into thesignaling message 704 is set to 11:20:30, which corresponds to thecurrent time 700 of 11:20:00 plus the 30 s time supervision period. Inthis example entity 1 100 may refer to a UE and the timer validityinformation corresponds to the time the subscriber indents to wait for aresponse to his telephone call request, so a reply from a B-party.

In the next step entity 2 102 may receive the signaling message 704called “Start Procedure”. It may contain the timer validity informationset to 11:20:30. As a signaling delay of two second between entity 1 100and entity 2 102 is assumed, the signaling message arrives 706 at11:20:02 time. Entity 2 102 may continue the communication procedure tothe entity 3 104, by sending a signaling message 710 called “ContinueProcedure”. Entity 2 102 may supervise the communication procedure andthe related supervision timer 708 is 15 s. So the timer validityinformation added by entity 2 102 to the signaling message 710 “ContinueProcedure” may be set to 11:20:17. In this example entity 2 102 mayrefer to a serving control entity of the called subscriber, which may bean S-CSCF in an IP Multimedia System (IMS) context. The serving controlentity of the called subscriber may try to deliver the terminating callto the first device of the subscriber, in this example entity 3 104,which may correspond to a fixed telephone. However, here it is assumedthat there is no response 712 from that fixed telephone, so no responseis received in entity 2 102 in during the supervision time 708 of 15seconds.

This may cause the time supervision 708 of the signaling message 710“Continue Procedure” to expire at a time 714 as indicated by the timervalidity information, so at 11:20:17. This may correspond to step 416 inFIG. 4. Entity 2 102 may then determine the next step of thecommunication procedure. In this example where entity 2 102 correspondsto a serving control entity of the called subscriber, the next step ofthe communication procedure may be to try to deliver the terminatingcall to the second device of the subscriber, in this example entity 4106, which may correspond to a mobile telephone. So entity 2 102 maycontinue the communication procedure to the entity 4 106, by sending asignaling message 718 called “Continue Procedure”. Entity 2 102 maysupervise the communication procedure and the related supervision timer716 may be 15 s. However, since the current time 714 is already11:20:17, the supervision time 11:20:17+15 s=11:20:32, which would bepast the expiry of the received timer validity information of 11:20:30.So in this case the entity 2 102 may set the outgoing timer validityinformation to the received timer validity information of 11:20:30. Sothe timer validity information added by entity 2 102 to the signalingmessage 718 “Continue Procedure” may be set to 11:20:30.

Here we assume that also on the mobile telephone there is no reply 720.At 724 11:20:30 the time supervision of the received timer validityinformation may expire. This may correspond to steps 500 to 504 of FIG.5a . The communication procedure may be terminated 724 in entity 2 102and no response is returned to entity 1 100. In parallel to this thetimeout 722 of the supervision timer may happen also in entity 1 100 andthe communication procedure may be terminated also in entity 1 100. So aUE corresponding to entity 1 100 may inform the subscriber that thedestination does not respond.

There may be further devices in use by the called B-subscriber, and justtwo devices may have been tried, entity 3 104 and entity 4 106. But asthere may be no time left, no further devices have been contacted. Dueto the timer validity information, entity 2 102 may exactly determinewhen to stop trying to deliver the terminating call. There are nooverdue responses, which cause inconsistencies in the network, whenentity 1 100 still receives responses for a communication procedure thathas terminated already.

Referring to FIG. 8, a method in a system for handling time supervisionin a communication network will be explained.

This scenario shows a case where a UE 800 may set up an emergencysession, the UE 800 corresponding to a first entity 100. The emergencysession may be handled by an E-CSCF 802 corresponding to a second entity102. In order to determine the nearest Public Safety Answering Point806, PSAP, the E-CSCF may involve a Location Register Function 804, LRF,which may be a database for looking up the closest PSAP for a givengeographical position of a UE 800. The LRF 804 may correspond to a thirdentity 104. Finally the emergency call may be forwarded to the closestPSAP for handling of the emergency case; the closest PSAP may correspondto a fourth entity 106.

The emergency session setup procedure may be started at the UE 800 at atime 810 of 11:20:00, referring to 11 o'clock, 20 minutes and zeroseconds. The communication procedure may to be time supervised and therelated supervision timer 812 may be 10 s referring to 10 seconds. Acorresponding signaling message 814 called “Emergency Session Setup” maybe sent from the UE 800 to the E-CSCF 802. The UE 800 may include thetimer validity information into the signaling message 814. In this casethe communication procedure may be valid from 11:20:00 for 10 seconds.So the UE 800 may await a corresponding response to the signalingmessage 814 called “Emergency Session Setup” within the time supervisionperiod 812. The timer validity information set by the UE 800 and addedinto the signaling message may be set to 11:20:10, which corresponds tothe current time of 11:20:00 plus the 10 s time supervision period.

In the next step the E-CSCF 802 may receive the signaling message 814called “Emergency Session Setup”. It may contain the timer validityinformation set to 11:20:10. As a signaling delay of one second betweenUE 800 and E-CSCF 802 is assumed, the signaling message may arrive 816at 11:20:01 time. The E-CSCF 802 may have now to determine theresponsible PSAP closest to the geographical position of the UE 800. Forthis the E-CSCF 802 may continue the communication procedure to the LRF804, by sending a signaling message 820 called “Determine PSAP”. TheE-CSCF 802 may supervise the communication procedure and the relatedsupervision timer 818 may be 15 s. Also here the supervision time wouldbe too long, so the E-CSCF 802 may forward the received timer validityinformation set to 11:20:10 to the LRF 804.

It is assumed here that there may be some bigger emergency case and theLRF 804 may be overloaded, so cannot deliver the responsible PSAP resultresponse. The E-CSCF 802 may monitor the supervision time 818 and maydetermine 822 at 11:20:07 that the timer is to expire soon. Based on theknowledge that the signaling delay between the nodes 800-806 may be onesecond, reaching a PSAP 806, returning a response to the E-CSCF 804 andreturning the response to the UE 800 would take 3 seconds, the thresholdmay be set to 3 seconds before expiry of the time supervision 818. Thismay correspond to steps 600 and 602 of FIG. 6.

Since no closest PSAP could be determined in time, the emergency sessionsetup request 826 may be forwarded to the default PSAP 806. This defaultPSAP 806 may be defined in the E-CSCF 802 by operation and maintenancemeans by the operator of the E-CSCF 802. Also this signaling message 826called “Emergency Session Setup” may be time supervised 824 and therelated supervision timer may be 15 s. Also here the supervision timewould be too long, so the E-CSCF 802 may forward the received timervalidity information set to 11:20:10 to the default PSAP 806.

The default PSAP 806, for example by checking the received timervalidity information, may prioritize this emergency request 826 andreplies 828 promptly. The corresponding response signaling message 828is transferred 830 via the E-CSCF 802 to the UE 800 and may arrive stillin time at the UE 800.

Referring to FIG. 9, an entity in a system for handling time supervisionin a communication network will be described. The illustrated entity maycorrespond to the entity 1 100 illustrated in FIG. 1. The entity 1 100may be adapted to perform one or more steps of the above describedmethod shown in FIG. 3.

The entity 1 100 may comprise a number of functional units, which aredescribed in further detail below and which are adapted to performrespective method steps.

For example, the entity 100 may be a network node such as a MSC, or aCSCF, or a SGSN, or a MME, or by alternative a UE.

A processing unit 900 of the entity 1 100 may be adapted to determinewhether a communication procedure is to be started which requires timesupervision. The processing unit 900 may further be adapted to determinethe current time with the help of the system clock unit 908 andcalculate a timer validity information based on the current time and atime supervision period associated with the communication procedure. Theprocessing unit 900 may further be adapted to compose a signalingmessage related to the communication procedure, the signaling messagecomprising the timer validity information, and send the signalingmessage via the sending unit 902 to an entity 2 102. The processing unit900 may further be adapted to time supervise the reception of a responseto the signaling message with the help of the time supervision unit 910.The processing unit 900 may further be adapted to receive and analyze aresponse from an entity 2 102 with the help of the receiving unit 904.The processing unit 900 may further be adapted to terminate thecommunication procedure at expiry of the time supervision period or thereception of a response to the signaling message. In a practicalimplementation the processing unit 900 may be one processor taking careof all the above functions, or may also be distributed over more thanone processor, wherein the functions are distributed over the availableprocessors.

The entity 1 100 may further comprise a sending unit 902 and a receivingunit 904 via which the entity 1 100 can communicate with an entity 2102, or with other entities of the communication network. The sendingunit 902 may send out signaling messages composed by the processing unit900. The receiving unit 904 may receive signaling messages originatingfrom other entities of the communication network, and forward thereceived signaling messages to the processing unit 900 for handling.

The entity 1 100 may also comprise a storing unit 906 for storinginformation related to the handling of timer supervision. The storingunit 906 may comprise various types of memory such as volatile memory,non-volatile memory, hard disk drives, solid state drives, a networkinterface to a database or a data center, secure digital cards, orhardware such as smart cards, non-reversible chips, security chips,security modules, or trusted platform module devices. The storing unit906 may be used by the procession unit 900 to store information, forexample a timer validity information, a communication procedure state,or program code.

The entity 1 100 may also comprise a system clock unit 908 for provisionof the current time. The current time may be fetched by this systemclock unit 908 from a NTP server located in the communication network orthe Internet. For interfacing the NTP server, the sending unit 902 andreceiving unit 904 interfaces may be used, or a separate interface maybe utilized. By alternative, the system clock unit 908 may host anatomic clock, or a Global Positioning System (GPS) based time receiver,or radio-controlled clock that is synchronized by a time code bit streamtransmitted by a radio transmitter connected to a time standard such asan atomic clock to obtain the current time. The current time may berequested by instructions from the procession unit 900.

The entity 1 100 may also comprise a time supervision unit 910 forsupervising timers running in the entity 1 100. A timer may for examplebe implemented by a periodic interrupt signal from the system clock unit908 and a counter, or by the processor clock of the procession unit 900and a shift register. The time supervision unit 910 performs the timesupervision of signaling messages sent to the entity 2 102. A timer inthe time supervision unit 910 may be instantiated, started, stopped,reset, and removed by instructions from the procession unit 900.

Referring to FIG. 10, an entity in a system for handling timesupervision in a communication network will be described. Theillustrated entity may correspond to the entity 2 102 or entity 3 103illustrated in FIG. 1, or entities 102-108 of FIG. 2. The entities maybe adapted to perform one or more steps of the above described methodshown in FIG. 4, 5 a, 5 b, or 6.

The entities 102-108 may comprise a number of functional units, whichare described in further detail below and which are adapted to performrespective method steps.

For example, the entities 102-108 may be network nodes such as a MSC, ora CSCF, or a SGSN, or a MME, or by alternative a UE.

A processing unit 1000 of the entities 102-108 may be adapted to receivea signaling message via receiving unit 1004, 1008 interfaces related toa communication procedure, the signaling message comprising a firsttimer validity information. The processing unit 1000 may further beadapted to determine whether the communication procedure is to becontinued, requiring sending of a further signaling message to a furtherentity of the communication network, the further signaling messagerequiring time supervision. The processing unit 1000 may further beadapted to determine the current time with the help of the system clockunit 1012 and calculate a second timer validity information based on thecurrent time and a time supervision period for the further signalingmessage. The processing unit 1000 may further be adapted to compose afurther signaling message related to the communication procedure andsend it to a further entity in the communication system via a sendingunit 1002, 1006 interface, the further signaling message comprising thetimer validity information. The processing unit 1000 may further beadapted to time supervise with the help of the time supervision unit1014 the reception of a response to the signaling message. Theprocessing unit 1000 may further be adapted to determine the terminationof the communication procedure if a supervision period of the furthersignaling message expires after expiration of the first timer validityinformation. The processing unit 1000 may further be adapted todetermine that a remaining time period before expiry of the first timervalidity information reaches a threshold. The processing unit 1000 mayfurther be adapted to compose and send a response associated with thesignaling message related to the communication procedure via a sendingunit 1002, 1006 interface. In a practical implementation the processingunit 1000 may be one processor taking care of all the above functions,or may also be distributed over more than one processor, wherein thefunctions are distributed over the available processors.

The entities 102-108 may further comprise a sending unit 1002 and areceiving unit 1004 via which the entities 102-108 can communicate withother entities 100-108, or with other entities of the communicationnetwork. The sending unit 1002 may send out signaling messages composedby the processing unit 1000. The receiving unit 1004 may receivesignaling messages originating from other entities of the communicationnetwork, and forward the received signaling messages to the processingunit 1000 for handling. The entities 102-108 may further comprise asecond sending unit 1006 and a second receiving unit 1008 via which theentities 102-108 can communicate with other entities 100-108, or withother entities of the communication network. The second send/receiveinterface complements the first send/receive interface and may performthe same functions. By alternative, the entities 102-108 may compriseonly a single send/receive interface.

The entities 102-108 may also comprise a storing unit 1010 for storinginformation related to the handling of timer supervision. The storingunit 1010 may comprise various types of memory such as volatile memory,non-volatile memory, hard disk drives, solid state drives, a networkinterface to a database or a data center, secure digital cards, orhardware such as smart cards, non-reversible chips, security chips,security modules, or trusted platform module devices. The storing unit1010 may be used by the procession unit 1000 to store information, forexample a timer validity information, a communication procedure state,or program code.

The entities 102-108 may also comprise a system clock unit 1012 forprovision of the current time. The current time may be fetched by thissystem clock unit 1012 from a NTP server located in the communicationnetwork or the Internet. For interfacing the NTP server, the sendingunits 1002, 1006 and receiving units 1004, 1008 interfaces may be used,or a separate interface may be utilized. By alternative, the systemclock unit 1012 may host an atomic clock, or a Global Positioning System(GPS) based time receiver, or radio-controlled clock that issynchronized by a time code bit stream transmitted by a radiotransmitter connected to a time standard such as an atomic clock toobtain the current time. The current time may be requested byinstructions from the procession unit 1000.

The entities 102-108 may also comprise a time supervision unit 1014 forsupervising timers running in the entities 102-108. A timer may forexample be implemented by a periodic interrupt signal from the systemclock unit 1012 and a counter, or by the processor clock of theprocession unit 1000 and a shift register. The time supervision unit1014 performs the time supervision of signaling messages sent to theentities 102-108. A timer in the time supervision unit 1014 may beinstantiated, started, stopped, reset, and removed by instructions fromthe procession unit 1000.

According to another embodiment, a computer program is provided. Thecomputer program may be executed by the processing units 900 and/or 1000of the above mentioned entities 100-108 such that a method for handlingtime supervision as described above with reference to FIGS. 2 to 8 maybe carried out or be controlled. In particular, the entities 100-108 maybe caused to operate in accordance with the above described method byexecuting the computer program.

The computer program may be embodied as computer code, for example of acomputer program product. The computer program product may be stored ona computer readable medium, for example a disk or the storing unit 906and/or 1010 of the entities 100-108, or may be configured asdownloadable information.

One or more embodiments as described above may enable at least one ofthe following technical effects:

Entities may set specific timer values and may have a possibility tocommunicate the specific timer values to the next entity of thecommunication procedure and by that increase the level of understandingfor the receiving entity how to handle time supervision.

In communication networks deploying the claimed entities and methodsthere may be no/less need for manual coordination of timers across theentities of the communication network.

A communication procedure may not time out backwards in the chain due tosome timers in entities expire and signaling messages are stillforwarded to the final destination.

Entities may be able to take intelligent decisions if to terminate acommunication procedure if timers will soon expire and by that limitunnecessary signaling and usage of network resources and resources inthe entities.

Modifications and other embodiments of the disclosed invention will cometo mind to one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is to be understood that the embodiments are not to belimited to the specific embodiments disclosed and that modifications andother embodiments are intended to be included within the scope of thisdisclosure. Although specific terms may be employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation.

The invention claimed is:
 1. A method for handling time supervision in acommunication network comprising a plurality of entities, the methodcomprising: receiving, by a second entity, a first signaling messageassociated with a communication procedure from a first entity, the firstsignaling message containing a first timer validity information;determining, by the second entity, whether a further processingcondition for performing a further step of the communication procedureis fulfilled, the further processing condition being associated with thefirst timer validity information, wherein the further processingcondition is associated with any one of the following conditions:expiry, before expiry of the first timer validity information, of asupervision timer supervising the reception of a response to a signalingmessage associated with the communication procedure; expiry of the firsttimer validity information; reception, before expiry of the first timervalidity information, of a response to a signaling message associatedwith the communication procedure; and determining that a remaining timeperiod before expiry of the first timer validity information reaches athreshold.
 2. The method of claim 1, wherein the further step of thecommunication procedure is any of the following: sending, by the secondentity, a further signaling message associated with the communicationprocedure to a further entity of the plurality of entities of thecommunication network, the further signaling message containing afurther timer validity information; sending, by the second entity, afurther signaling message associated with a further communicationprocedure to a further entity of the plurality of entities of thecommunication network, the further signaling message containing afurther timer validity information; sending, by the second entity, aresponse to the first signaling message to the first entity; andterminating, by the second entity, the communication procedure.
 3. Themethod of claim 2, wherein, if a supervision period of the furthersignaling message expires before expiration of the first timer validityinformation, the second timer validity information is set equal to acurrent time plus a supervision period of the further signaling message,or else the second timer validity information is set equal to the firsttimer validity information.
 4. The method of claim 3, further comprisingdetermining, by the second entity, that a remaining time period beforeexpiry of the first timer validity information reaches a threshold,wherein the threshold for remaining time period before expiry of thefirst timer validity information in the second entity is based on asignaling delay time for a signaling message to traverse between thefirst entity and the second entity of the communication network.
 5. Themethod of claim 1, wherein the timer validity information indicates anabsolute point in time comprising year, date, time, and time zoneinformation.
 6. The method according to claim 1, comprising:determining, by the first entity, whether a supervision condition forsupervising the communication procedure is fulfilled; and based on aresult of the step of determining whether the supervision condition isfulfilled, adding, by the first entity, the timer validity informationto the first signaling message, and sending the first signaling messageto the second entity.
 7. The method according to claim 6, wherein thesupervision condition is associated with a type of the communicationprocedure.
 8. A network entity for handling time supervision in acommunication network comprising a plurality of entities, the networkentity comprising: one or more processing circuits configured to causethe network entity to: receive a first signaling message related to acommunication procedure, the first signaling message comprising a firsttimer validity information; determine a further step of thecommunication procedure; determine a current time; determine a timesupervision period associated with a further signaling message relatedto the communication procedure or to a further communication procedure;determining a second timer validity information based on the currenttime and the time supervision period for the further signaling message;send the further signaling message to a further entity in thecommunication system, the further signaling message comprising saidsecond timer validity information; time supervise a reception of aresponse to the further signaling message; terminate the communicationprocedure at expiry of the first timer validity information; determiningthat a remaining time period before expiry of the first timer validityinformation reaches a threshold, and sending a response associated withthe first signaling message related to the communication procedure,based on the reception of a response to the further signaling message.9. The network entity of claim 8, wherein the one or more processingcircuits are configured to cause the network entity to: determinewhether a supervision condition for supervising the communicationprocedure is fulfilled; and based on a result of the determining whetherthe supervision condition is fulfilled: add the timer validityinformation to the first signaling message, and send the first signalingmessage to the second entity.
 10. A system for handling time supervisionin a communication network comprising a plurality of entities, thesystem comprising at least one network entity, and a further networkentity for handling time supervision in a communication networkcomprising a plurality of entities, the network entity being capable of:determining whether a communication procedure is to be started whichrequires time supervision; determine a current time; determine a timesupervision period associated with the communication procedure; send asignaling message related to the communication procedure, the signalingmessage comprising the timer validity information based on the currenttime and the time supervision period; time supervise the reception of aresponse to the signaling message; terminate the communication procedureat expiry of the time supervision period; and finish the communicationprocedure in response to the reception of a response to the signalingmessage.
 11. A computer program product which, when being executed byone or more processing circuits of a second entity, causes the secondentity to: receive a first signaling message associated with acommunication procedure from a first entity, the first signaling messagecontaining a first timer validity information; and determine whether afurther processing condition for performing a further step of thecommunication procedure is fulfilled, the further processing conditionbeing associated with the first timer validity information, wherein thefurther processing condition is associated with any one of the followingconditions: expiry of a supervision timer supervising the reception of aresponse to a signaling message associated with the communicationprocedure, before expiry of the first timer validity information, expiryof the first timer validity information, reception of a response to asignaling message associated with the communication procedure, beforeexpiry of the first timer validity information, or determining that aremaining time period before expiry of the first timer validityinformation reaches a threshold.